By Matt McGrath
BBC science reporter
The reptile possessed primitive and more advanced traits
Researchers in China and the UK say they have discovered the fossils of a new type of flying reptile that lived more than 160 million years ago.
The find is named Darwinopterus, after Charles Darwin.
Experts say it provides the first clear evidence of a controversial idea called modular evolution.
The 20 new fossils found in north-east China show similarities to both primitive and more advanced pterosaurs, or flying reptiles.
The research is published in the journal, Proceedings of the Royal Society B.
Pterosaurs were flying reptiles that flourished between 65 and 220 million years ago.
Darwinopterus could offer evidence of modular evolution
Until now, scientists had known about two distinct groups of these creatures - primitive, long-tailed pterosaurs and more advanced short-tailed ones, separated by a gap in the fossil record.
But the discovery of more than 20 new fossil skeletons in north-east China sits in the gap in this evolutionary chain.
Darwinopterus is a hawk-like reptile with a head and neck just like advanced pterosaurs - but the rest of the skeleton is similar to more primitive forms.
Researchers say that this could be evidence of what they call modular evolution - where natural selection forces a whole series of traits to change rapidly rather than just one.
"Darwinopterus came as quite a shock to us" said Dr David Unwin, from the University of Leicester, UK.
"We had always expected a gap-filler with typically intermediate features such as a moderately elongate tail - neither long nor short.
"But the strange thing about Darwinopterus is that it has a head and neck just like that of advanced pterosaurs, while the rest of the skeleton, including a very long tail, is identical to that of primitive forms."
With its long jaws and rows of sharp-pointed teeth, these creatures were very well suited to catching and killing other flying species.
The fossils were found in rocks that are 160 million years old, making them 10 million years older than the first bird, Archaeopteryx.
Dr Unwin collaborated on the study with researchers from the Geological Institute in Beijing, China.